Molybdenite outshines silicon and graphene for electronic applications
By Darren Quick
February 1, 2011
Researchers have uncovered a material that they say has distinct advantages over traditional silicon and even graphene for use in electronics. Called molybdenite (MoS2), this mineral is abundant in nature and is commonly used as an element in steel alloys or, thanks to its similarity in appearance and feel to graphite, as an additive in lubricant. But the mineral hadn’t been studied for use in electronics, which appears to have been an oversight with new research showing that molybdenite is a very effective semiconductor that could enable smaller and more energy efficient transistors, computer chips and solar cells.
Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) say one of molybdenite’s advantages over silicon is its thinness. With an atomic structure consisting of a sheet of molybdenite atoms sandwiched between sheets of sulfur atoms, molybdenite is less voluminous than silicon.
“It’s a two-dimensional material, very thin and easy to use in nanotechnology. It has real potential in the fabrication of very small transistors, light-emitting diodes (LEDs) and solar cells,” says EPFL Professor Andras Kis. “In a 0.65-nanometer-thick sheet of MoS2, the electrons can move around as easily as in a 2-nanometer-thick sheet of silicon,” adds Kis, “but it’s not currently possible to fabricate a sheet of silicon as thin as a monolayer sheet of MoS2.”
Additionally, to turn a transistor on and off, a semi-conductor with a “gap” must be used and molybdenite’s 1.8 electron-volt gap is ideal for this purpose. It would allow transistors to be made that consume 100,000 times less energy in standby state than traditional silicon transistors.
But it’s not just silicon that is humbled by molybdenite. Everyone’s favorite wonder material graphene also gets a going over. In semi-conductors, electron-free spaces exist between bands of energy. These so-called “band gaps” allow certain electrons to hop across the gap if it is not too small or too large. This results in a greater level of control over the electrical behavior of the material as it can easily be turned on or off. The existence of such a gap in molybdenite gives it a distinct advantage over graphene, which has no such gap and it is difficult to artificially produce one in the material.